Stanford Financial Group, a firm run by wealthy financier Sir Allen Stanford that says it manages $51bn (€39.6bn), is being examined by the Securities and Exchange Commission and two other regulatory agencies, according to the firm.

Regulators from the SEC, the Financial Industry Regulatory Authority and the Florida Office of Financial Regulation visited six branch offices of Stanford Financial's broker-dealer firms last month. The examination has been going on for at least several months, according to a person familiar with the matter. The visit by regulators was previously reported by Business Week.

The focus of the probe isn't clear. Stanford's firm offers many financial services, chief among them wealth management services, and markets certificates of deposit through his offshore bank, Stanford International Bank, in Antigua. The CDs offer unusually high and consistent returns. Stanford controls both the bank and the financial group that markets the CDs the bank issues.

Representatives for Finra and the SEC declined to comment. Florida regulators did not return calls for comment.

Stanford is a prominent businessman whose wealth was estimated last year as $2.2bn by Forbes magazine. He lives in St. Croix, US Virgin Islands.

In an email to Stanford employees sent Thursday, Stanford said regulators have told his firm their visits were part of a routine examination and that he is co-operating. In the email, he casts the examination as a sign of the sour economic times and one that comes "after the regulatory deficiencies of the last decade."

According to the bank's website, the bank earns income from credit facilities and fees and the majority of its assets are invested in globally diversified portfolios.

One investor who has CDs with the bank said it has the right to refuse early redemptions on the CDs. A spokesman for Stanford Financial would not comment on early redemptions.

In his email to employees at Stanford Financial, Stanford also cites two "disgruntled employees" whom he claimed have "gone to the regulators questioning our work and our process. . . . This could have compounded an otherwise routine examination." He did not name the employees.

Last year, two Stanford Financial employees, D. Mark Tidwell and Charles W. Rawl, filed an employment-discrimination suit in Texas state court alleging Stanford Financial was engaging in "various unethical and illegal business practices, including overstating the asset value of individuals in a manner designed to mislead potential investors and purging electronic data from its computers in response to an investigation by the Securities & Exchange Commission," according to court documents.

Neither Tidwell nor Rawl nor their attorney returned calls for comment. A Stanford Financial spokesman declined to comment on the suit.

-- Write to Dionne Searcey at dionne.searcey@wsj.com and Annelena Lobb at annelena.lobb@wsj.com